Cryopreservation in trehalose preserves functional capacity of murine spermatogonial stem cells

Effect of sugar molecules on the cryopreservation of mouse spermatogonial stem cells

OBJECTIVE

To study the influence of sugars and establish a serum-free freezing method for the cryopreservation of spermatogonial stem cells (SSCs).

DESIGN

Animal study.

SETTING

University laboratory.

ANIMAL(S)

C57BL/6-TgEGFP, C57BL/6 mice.

INTERVENTION(S)

Germ cells enriched from testis cells were frozen using standard freezing medium containing sugars, including monosaccharides, disaccharides, and trisaccharides at 50, 100, and 200 mM, respectively. To study the feasibility of establishing a serum-free freezing method, fetal bovine serum was substituted with knockout serum replacement.

MAIN OUTCOME MEASURE(S)

Freeze-thawed germ cells were evaluated for recovery rate, proliferation capacity, and stem cell activity after transplantation to recipient testes.

RESULT(S)

Supplementation of freezing medium with 200 mM disaccharide is an effective method for cryopreservation of SSCs. Trehalose is the most effective cryoprotectant among all the sugars tested and only lactose was comparable to trehalose. Our proliferation and transplantation data show that serum-free freezing can be achieved in freezing medium supplemented with 200 mM trehalose, 10% knockout serum replacement, and 10% dimethyl sulfoxide (DMSO) for cryopreservation of SSCs.

CONCLUSION(S)

These findings raise the possibility of effectively banking frozen SSCs from various species, including humans, in a traditional serum-free medium for germ cell research and male infertility treatments.

Cryopreservation of mouse spermatogonial stem cells in dimethylsulfoxide and polyethylene glycol

Assisted reproductive techniques involving isolation, culture, and transplantation of spermatogonial stem cells (SSCs) have the potential to create transgenic livestock and to treat male infertility caused by cancer treatments such as chemotherapy or radiation. Because stem cells may need to be preserved for several years before reintroduction to the patients' testes, efficient SSC cryopreservation techniques need to be developed. SSCs can reinitiate spermatogenesis in recipient testes after freezing; however, optimal cryopreservation protocols have not been identified. The objective of this study was to develop an efficient cryopreservation method for SSCs using permeable cryoprotectant agents (PCAs) or additive cryoprotectant agents (ACAs). To identify an efficient cryopreservation method, populations of mouse testis cells enriched for SSCs were cultured in vitro and frozen using conventional freezing media containing various PCAs or ACAs for 1 wk or 1, 3, 6, 12, or 24 mo. Additionally, various molecular weights and concentrations of polyethylene glycol (PEG) were evaluated. Recovery rate, culture potential, and stem cell activity were significantly greater for cells frozen in 2.5% PEG with a molecular weight of 1000 compared to other treatment groups. These cells also retained the ability to colonize recipient testes, generate normal spermatogenesis, and contribute to viable offspring. The systematic analysis of many cryoprotectant agents indicates that 2.5% PEG (molecular weight 1000) is the most effective agent for efficient SSC cryopreservation.